ABSTRACT
Organisms in the same population or species commonly cooperate and are altruistic to each other. This helps the population or species survive, maintaining biodiversity. It might appear that this contradicts natural selection, but a closer look shows otherwise. It can be accounted for by kin selection, reciprocal altruism, and perhaps group selection. Cooperative behaviors include not breeding, cooperative breeding, and alarm calls. Ritualized combat with signaling and communication avoids actual fighting, injury, and death. Although good for the population or group, it can be explained without the use of group selection by standard individual selection, with the organisms in conflict with each other acting in their own interests. This can be shown with a type of mathematics called game theory, which shows that the best strategy is used by the retaliator, and called tit for tat. The individuals of some populations work so closely together as to act in many ways like a single organism, and this is called a superorganism, which some think has a group brain. Examples are colonies of highly social bees and ants and human societies.
